Apparatus for building tires



Nov. 30, 1948. w. J. BRETH APPARATUS FOR BUILDING TIRES 16 Sheets-Sheet 1 Filed June 14, 1944 INVENTOR WALTER J. BRETH ATTORNEYS Nov. 30, 1948. w. J. BRETH APPARATUS FOR BUILDING TIRES Filed June 14, 1944 16 sheets sheet 2 m' I a" INVENTOR WALTER .1. BRETH tlvww v ATTORNEYS v Nov. 30, 1948. w. J. BRETH APPARATUS FOR BUILDING TIRES 16 Sheets-Sheet 3 Filed June 14, 1944 w 3 B w M 2% 8x mm Nw /Gv I Q Nov. 30, 1948.. w. J. BRETH APPARATUS FOR BUILDING TIRES Filed June 14, 1944 l6 Sheets-Sheet 4 INVENTOR WALTER J. BRETH MN QM Na w, 1948. BRE H 2,455,038

v APPARATUS FOR BUILDING TIRES Filed Juhe 14, 1944 I 16 Sheets-Sheet 5 vii/111111! 'VIIIIIIIIIIII INVENTOR -99 WALTER J BRETH ATTORNEYS Nov. w, 1948. w 4 BR TH v 2,455,038

APPARATUS FOR BUILDING TIRES Filed June 14, 1944 A 16 Sheets-Sheet 6 B If; 1 40 ""zzztzrzz: 7 l I I E g a I I 55 I L 7' INVIZNTOR WALTER J. B'RETH BY M 1 ATTORNEYS Nov. 30. 1948. .w, BRET 2,455,038

APPARATUS FOR BUILDING TIRES Filed June 14, 1944 16 Sheets-Sheet 8 INVENTOR WALTER J. BRETH ATTORNEYS Nov. 30, 1948. w. J. BRETH 2,455,038

APPARATUS FOR BUILDING TIRES Filed June 14, 1944 16 Sheets-Sheet 9 INVENTOR ATTORNEYS WALTER J. BRETH Nov. 30, 1948. w. J. BRETH APPARATUS FOR BUILDING TIRES- l6 Sheets-Sheet 10 Filed June 14, 1944 INVENTOR WALTER J. BRETH BY 5m 71: ATTOKNEYS 67' l6 Sheets-Sheet 11 Filed June 14, 1944 l i i y i l l M i i J M M INVENTOR H m n R mm a +m m R ,T n A A m w. J. BRETH 2,455,938

APPARATUS FOR BUILDING TIRES Nov. 30, 948.

Filed June 14, 1944 16 Sheets-Sheet 12 INVENTOR WALTER J BRETH Pi E5 BY ATTORNEYS Nov. 30, 1948.

W. J. BRETH APPARATUS FOR BUILDING TIRES Filed June 14,1944

16 Sheets-Sheet 15 INVENTOR WALTER J. BRETH BY W ATTORNEYS Nov. 30.- 1948. i v w. J. BRETH 2,455,038

APPARATUS FOR BUILDING TIRES Filed June 14, 1944 16 Sheets-Sheet 14 ENVENTOR WALTER J. BRETH BY /M 1- 2(8 4? ATTORNEYS Nov. 30, 1948. w. J. BRETH APPARRTUS FOR BUILDING TIRES 1e Sheets-Sheet 15 Filed June 14, 1944 Nov. 30, 1948. w. J. BRETH APPARATUS FOR BUILDING TIRES Filed June' 14, 1944 16 Sheets-Sheet 16 5&3 ME

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i atented Nov. 30, 1948 APPARATUS FOR BUILDING TIRES Walter. J. Breth,,Ak1-on,, Ohio, assignor. to. The. General Tire & Rubber Company-g, Akron, Ohio,

a corporation of Ohio Aipplication. Jiune 14, 1944?.SerialrNo. 5140,3061

17 Claims. 1

The present invention relates to a method of and apparatus for building pneumatic tiresand issan improvement upon the method and apparatus of my Patent. 2,313,035 granted March 9, 1943.

. The present invention. has for an object to provideamethod by which tires of superior quality may be built more. rapidly.

.As further object: of theinvention is. to provide a. semieautomatic tire-building machine that is more compact, greatlysimplified in construction and which: is capable. of; operation. at highspeed- Aifurther object. of the inventionis. to provide a machine in which the weight'of reciprocating elements. is greatly reduced and in. which the friction of. moving parts is greatly lessened so that-the. machine may-be. operated by motors of lesshorsepower;

Further objects are. to. so. regulate the operations that simpler control. devices may be employed and sothat-single speed operating motors may be employed.

It .isalso'anobjectof the invention-to-provide anoperating; mechanism for theintermittently operating bead. forming, instruments that isposi tive in operation and that insures the. correct timing and sequence of operation- An" additional object of the inventionis-to provide animprovedmethod of. and mean-srfor folding the edgesof the inner fabric plies. over the.- ends of the drum.

A further object is to provide an. improved. means for. applyingthe rubber covering to fabric plies. previouslyv placed upon the-drum; and improved: means. for compacting thetire body and firmly aflixing together the fabric. plies andrubber. cover stock A. further object. is to provide fluid pressure actuators for cover stock applying and. tire compacting rollers together with. controlling means by. whichv the rollers-may be broughtinto engaging position in the proper sequence and applied. with. the. properpressures- With the above and other objects in View, the invention may. be saidto com-prisethe method of and apparatus for building pneumatic tires as illustrated in'the" accompanying drawings hereinafter described and particularly set forth in the appended claims together, withsuch variations and modifications thereof as" will be apparent to one. skilled in the art to which the invention pertains.

Reference should be had to the accompanying. drawings forming a part of this specification in which;

Fig. 1 is a fragmentary front elevation of a ti-re' building.- machine embodying the invention,

showing the. tire building drum, the stationary,

bead building; head:and.a portion of the movable bead ibuild-ing, head;

Fig. 2 is. atransverse. vertical. section taken on the line indicated at 2-2 in Fig. 1;

Fig... 3 is v a. fragmentary vertical axial; section through the. stationary head: and the adjacent.

endof the; drum Fig. 4 is a fragmentary section taken on the line indicated at 4-4-i-n Fig. 3;;

Fig. 5. is ariragmentary sideelevation showing one of.- the automatically operated control switches;

Fig.6 is'a topplan view of. thestationaryhead;

Fig; .7. is: a. vertical transverse section showingthe inner expansibl'e-nish.assemblyin side elevation; I

Fig. histasection taken omthe line indicated. at 88 in Fig. '7

Fig. his a. fragmentary side elevation of a portion of: theydisln assembly showing the inner diskin expanded position;

Fig;.1oris a. fragmentary section taken on the lineindicated at; III-1 0. in. Fig. 7, showing the stop for the spring actuated segments of the. intermediatedisk;

Figs.v 1.1. to 18.. inclusive are. sectional views showing. successive positions ofthefabric shaping and bead applying devices;

Fig... I-l: shows the resilient: fabric folding ring expanded position between. the bead support ing annulus and drum.

Fig-r12 shows in dotted lines the position of the fabric: folding ring after ithas been advanced to a position surrounding the projecting edge of the fabric band and, full lines, the position of the: ring aft'erit' has beenreleased and allowed to snapto contracted position against the exterior surface of the projecting edge of the fabric band and form inward-1y projecting fabric flange-overlying the end" of the drum;

Fig: 1 3" shows theapplication of the bead ring to the fabric flange overlying the end' of the drum;

Fig. shows theflipper' strip that is attached tothe beadring being presseddown on the fabric ofthe. drum;

Fig. 15 shows the operation by which the fabric is foldedoutwardly against the interior of the headline;

Fig; 16' shows the fabricbeing folded outwardlyagainst the outer. face of thebead' ring;

Fig. 17" shows, the pressing in of the fabric edge 3 against the drum shoulder outwardly of the bead ring;

Fig. 18 shows the movable parts of the bead building head in the retracted positions that they occupy during the application of the external fabric and rubber plies to the previously formed tire carcass on the drum;

Fig. 19 is a sectional view showing the external plies of fabric and rubber applied to the previously formed interior portion of the tire;

Fig. 20 is a diagrammatic end elevation showing the pressure and stitching rollers the external plies;

Fig. 21 is a section taken on the line indicated at -4! in Fig. 20 showing the mainpressure rollers engaging the external" rubber covering of the tire;

Fig. 22 is a transverse section'through'one of the deformable pressure rollers taken on the line indicated at 22-22 in Fig. 21;

Fig. 23 is a fragmentary section taken on the line indicated at 2323 in Fig.20, showing the bead stitching rollers in engagement with the ex-' ternal fabric plies overlying the bead ring;

Fig. 24 is a fragmentary plan view of the bead stitching rollers viewed as indicated at 24-24 in Fig. 20; Y

Fig. 25 is a section taken on the line indicated at 2525 in 'Figi 20' showing the tread shaping rollers engaging the shoulders of the tread portion of the tire;

Fig. 26 is a verticaltransverse section through the machine, taken on'the line indicated at 2B' 26 in Fig. land showing the pressure roll supports and actuators in side elevation;

Fig-27 is a sectional view, showing the operation by' which the outer fabric plies are folded against the interior of the bead;

Fig. 28 is a sectional view showing the final pressing of the fabric against the'interior of the bead;

v Fig. 29 is a sectional view showing a bead ring in position to betransferred toitsseat on the rigid bead applying annulus;

Fig.' 30 is a" sectional view, showing the operation by which the bead ring is transferred to its seat; i

Fig. 31 is a fragmentary axial section through the Geneva gears, employed for intermittently and sequentiallyioperating the movable parts of the bead building, head; if

Figs. 32, 33 and 34am fragmentary side elevations, each showing a different form of Geneva gear employed in the actuating mechanism;

Fig. 35 is a development in the plane of the sheet of the peripheries of the large Geneva gears, of the stationary bead building head, showing the arrangement of teeth thereon;

Fig. 36 is a development similar to Fig. 35,

showing the large Geneva gears of; the movable head; 1

Fig.3? is a combined wiring and the fluid pressure diagram, showing the means by which various operations performed by the machine are controlled.

The tire building machine of the present invention consists of a centrally disposed, collapsible tire building drum A which may be of the usual and conventional construction, a stationary bead buildinghead B and a movable bead building head C, which's'erve to apply the bead rings to fabric at the ends of the drum and to shape the bead. portions of the tire, the arrangement being similar to that disclosed .in my Patent No. 2,313,035 granted March 9, 1943. Since the engaging 4 mechanisms on the two heads B and C are identical, except for certain details of the operating and control devices, the mechanism of the stationary head B is illustrated completely herein, while only enough of the head C is shown to make clear the operative relationship.

The machine of the present invention is mounted upon an elongated base. I, upon which the head B and the drum A are mounted in fixed positions, and upon which the head 0 is slidably supported for movement axially toward and away from the drum A. The actuating and control mechanism of the head B is mounted within a housing 2 having vertical inner and outer and side walls- The drum A, which is composed of collapsible segments, is supported on a shaft 3 and a sleeve 4 on the shaft 3, the segments of the drum being connected by suitable links to the sleeve and shaft so as to be expanded or collapsed by relative rotary movements of the sleeve and shaft, Since this construction is conventional for tire building drums, the linkage is not herein illustrated.

The supporting shaft 3 is mounted in bearings 5 and B in the innerand outer walls of the housing 2, and has interfitting engagement with an axially aligned shaft 7 on the movable head C. The shaft 3 is driven by an electric motor 8, mounted on a bracket Qattached to the base I, the shaft 3 being connected to the motor 8 through sprocket chains In and H and an interposed reduction gearing in a housing l2, the reduction gearing being driven by the motor through the chain-i9 and the shaft 3 being driven from the reduction gearing through the chain ll. In order to cause relative rotation of the shaft 3 and sleeve i to collapse the drum, an air brake I3 is connected by a sprocket chain M to the sleeve 4. Upon application of the brake IS, the sleeve '4 is held against rotation, whereupon continued rotation of shaft 3 in one direction or the other will expand or collapse the drum.

A transverse actuating shaft I5 is journaled in the side Walls of the housing 2, and this shaft has a Worm wheel i6 attached thereto that meshes with a worm I! on a longitudinal shaft is journaled in the inner and outer walls of the housing. The moving parts of the bead building head are actuated by the shaft [5, which is driven by an electric motor ['9 through reduction gearing in a housing 20 and a sprocket chain 2| extending to the shaft [8.

The moving parts of the bead building head B are actuated by the shaft l5 and it is desirable that the rotation of this shaft be stopped upon excessive resistance to movement of any of these parts. The shaft is is, therefore, driven through a slip clutch 22 interposed between the sprocket chain 2! and the shaft I5. The shaft l8 preferably projects through the outer wall of the housing 2 and has a squared end 23 adapted to receive a hand crank by which the shaft may be turned manually to adjust the moving parts when desired.

Bead building devices The bead ring applying and bead forming instrumentalities of each of the bead building heads are annual members which engage with the bead ring and fabric throughout the circumference thereof. -These annual members are coaxial with and surround the shaft 3 and are mounted for axial movements with respect to the drum. An annulus 24 is carried by axially extending square bars 25 which, as best shown in Fig. 6,

are slidably mounted in the housing 2 and upon ances ries:

guides'26 atthe upper ends ofposts 21 mounted.

on: base i inwardly of. the housin as shovsm in Fig.1 2.. Axial movements are imparted. to the nected to the bars 25 and to cranks 29 on the ends of a transverse shaft 3o mounted in the housing 2 abovethe shaft 5. The rods 28 are connected to brackets: 31 attached to the tops of the bars 25 by bolts 32', the brackets 3| being provided with flanges 33: that project inwardly past the inner sides of the bars 25.

As shown in Fig. 3, a. bead ring: supporting annulus 3-4: is mounted for movement within the annulus 2'4 and is provided along its inner edge withza rabbeted bead ringseat 35. As shown. in Fig. 6,. supporting brackets 36- attached to the bead ring annulus '34 are slidable uponthe bars 25 and: carry rods 37 that extendalong the inner sides of the bar 25' and slide in apertures in the flanges 3-3 of the brackets 31-. Coil springs 38 surrounding the rods 31. are interposed between the brackets 3i and 36 and normally cause the bead supporting annulus to travel with the annulus 24-. However, when the inward movement of the bead supporting annulus is impeded, the springs so will yield and permit the annulus 24 to advance beyond the annulus M. In applying the bead ring the inward movement of the annulus 34 is stopped when the bead ring is pressed against an inwardly projecting bead positioning flange 39' on the end of the drum and the bead ring is held against the flange 39: with an increasing pressure as the annulus 26 is advanced over the end of the drum and the springs 38 are compressed. The annulus 24 carries a smoothing ring 4E!v in the form of an endless coil. spring, which is normally of a diameter less than that of the drum, but which is adapted to beexpanded to conform tothe periphery of the drum upon movement over the drum shoulder. The ring 40 is supported by a series of circumferentially spaced, radially disposed links 4! that are pivoted at their outer ends to the interior. of the annulus 24 to swing axially. The ring 40 serves to press down portions of the fabric overlying the shoulder portion of the drum. The springs 38 are of considerable length so that the movement of the annulus 25 over the end of the drum does not cause an excessive pressure to be exerted upon the bead by the annulus 34.

For folding the end edges of a band of fabric on the drum inwardly .over the shoulders of the v drum, each head is provided with a contractible endless coil spring folder ring 42 that is adapted to be expanded to a dimeter greater than that of the drum, and to be placed over an end portion of a fabric band that projects beyond the end of the drum and then contracted to fold the fabric inwardly over the drum shoulder. The contractib'le' endless coil spring ring 42 is carried by axially extending arms 43 that are rigidly attached to the outer ends of radial bars 44 that are slidably mounted in radially disposed dovetail slots 45 in the outer face of a disk 46 that is slid'ably mounted on the sleeve 4. Suitable means is provided for simultaneously imparting radial outward movements to the ring supporting arms 43 'to expand the ring 42 to a diameter greater than that of the drum. This movement is accomplished by means of a series of identical toggles, each consisting of an inner radially disposed link 41 pivoted to the hub of'the disk 46 and an outer radially disposed link 48 pivoted to the outer end of one'of the arms 43. The toggle links 4% and 4.8 are connected at their. outer and inner ends; respectively,: by pivots 49. and 51]. t0-

the inner endsof elongatedaxially extending actuating plates 51, which are pivotally connected,

at their outer, ends to a disk 52 that is mounted to slide axially upon a sleevev 53 that slides on the sleeve 4;. The movementof the disk 52 on the.

sleevetaisalimitedby acollar 54 on theouter, end of the sleevezandsby aflange; 55 at the inner end. of the sleeve. Movement may be imparted to the. disk52loy engagement. of the collar 54 or flange '55 therewith when the: sleeve 53. is shifted axially on'the: sleeve 4. The disk 45; is movedtoward and; away fromthe end of the drum by means of: axially" extending rods 56; attached to the disk,

and extending through the inner and outer Walls of the housing 2' and: pivotally connected to crank armsv 51;,- attached 'to a horizontal shaft 58 mountediin brackets 59 attached to the outer wall of thehousing 2. The sliding sleeve 53 is moved axially on the sleeve l by means of rods fill at.- tached: to the collar 54, extending axiallythrou'gh the mechanism housing 2v and pivotally conn'ectedv to crank arms-6i attached to a sleeve 62, rotatably mounted on the shaft 58.

The initial step in the building of a tire by the method of the present invention consists in applyinga band of fabric composed of a plurality of plies to the periphery of the drum. The fabric is applied to the drum in the usual and conventional manner and the width of the fabric band so applied is greater than the length of the drum, so that the edges of the band project a substantial distance beyond each endof the drum. The projecting ends of the fabric are then folded in against the ends of the drum by means of the contractible rings 42, after which the bead ring is pressed against the fabric over lying the flange .iiii of the drum, and is held in place by the attachment of a fabric flipper strip carried by the bead ring to the fabric on the periphery of the drum.

After the bead ring is secured in. place against the fabric on the shoulder of the drum, the portion of thefinwardly extending flange of fabric that projects past the interior of the bead ring is folded axially across the interior of the bead ring and radially outwardly over the outer face of the bead ring. The latter folding operations are performed by means of a disk assembly that is mounted to move axially into and out of the end of the drum. This disk assembly is supported upon a disk 63 that'slides on the sleeve 4 and comprises outer, inner and intermediate expansible disks 64, and 66, each of which is composed of radially movable segments. The disks 64, 65 and 6B are held in place between the main disk 63 and an inner retaining plate 61 that is secured to and spaced inwardly from the disk 63. The outer expansibledisk 64 bears against the inner face of the disk 63 and the inner expansible disk 65 has an offset inner por tion 68 that bears against the disk 65. The segments of the inner expansible disk 85, with their outer portions offset inwardly from the disk 64 provide a space between the outer portions of the disks 64 and 65 in which the intermediate expansible disk 66 is mounted, the disk fifi'having .a shouldersfifi lying within the annular disk 66.

Radial movements are imparted to the segments of the disk 64 by means of radially swinging links lfl that are pivoted at their outer ends to lugs H on the outer faces of the disk 64, and at their inner ends to lugs 12 on a collar 13 that is slidably mounted on the sleeve 4; Movements of thecollar I3 axially toward or away from the disk 63 causes the segmentsof the disk 64 to be simultaneously moved radially outwardly or inwardly to expand or contract the disk.

The disk 63 is moved axially. by means of a pair of rods 74 that extend axially and have reduced outer ends 15 that are telescopically received in the tubular ends of alined rods I6 as shown in Fig. 6. The reduced end I ofeach rod I4 carries a pin 18 that engages in a longitudinal slot 79 in the tubular end of the rod I6 and a coil spring 80 surrounds the reduced portion I5 between the rod 16 and the shoulder on the rod I4 at the inner: endof the reduced portion I5. The rods I6 are pivotally connected to crank arms 8I attached to a horizontal shaft 82 mounted on the inner wall of thehousing 2. Rocking movement of the shaft 82 moves the disk 63 inwardly or outwardly with respect to the drum, through the telescopically connected :rods "I4 and IS, the spring 80 permitting relative movement between the rods I4 and. I6 so'that a gradually increasing pressure maybe applied to the disk 63 when inward movement thereof is impeded.

The collar I3 is connected. by tie rods 83 to a collar 84 mounted on the sleeve 4, outwardly of the slidable sleeve 53, the tie rods 83 extending through the disks S3 and 52 and the collar 54, as shown in Fig. 3. Collars 73 and 84 are shifted axially by means of rods 85 attached to the collar 84 and to crank arms 86 on a sleeve 81 that is rotatably mounted on the horizontal shaft 82, as shown in Fig. 6. By actuation of the crank arms 86, the collar I3 may be moved axially toward or. away from the disk 63 to expand or retract the outer disk 64. l

Inwardly of'the inner portion 68 of the expansible disk 65, a ring 88 is secured to the disk 63 by means of bolts 89, as best shown in Figs. 7, 8 and 9. The bolts 89 are secured to the disk 53 and extend through arcuate slots 90 in the ring 83, so that the ring 38* may have a limited turning movement on the disk 63. The ring 88 has gear teeth 9| formed on a portion of its outer periphery. These teeth mesh with apinion 92 thatis keyed to a shaft 93 that extends axially, the pinion 92 having a hub 94 journaled in the disk 63. The hub 94 projects outwardly through the disk Y63 and carries a collar 95 that bears against the outer face of the disk to hold the pinion in mesh with the.teeth 9| and against the inner face of the disk 53. The collar 95 is secured to the hub and thehub to the shaft 93 by means of set screw 96 threaded in the collar 95 and hub 94 and hearing at its irmer end against the shaft 93. The shaft93 has a squared outer end 91 that slidably fits in the hub 98 of an actuating arm 99 that is operated by the plunger I89 of a fluid pressure cylinder IN, the hub 38 being journaled in a fixed bearing member I02 and being held against endwise movement with respect to the bearing member by a shoulder I 53 and a collar 84 that engage with opposite sides of the bearing member.

Turning movements of the ring 88 imparted thereto by the fluid pressure cylinder IBI through the arm 99, shaft 93 and pinion 92, serve to impart radial movements to the segments of the inner disk 65, the ring 88 being connected to the segments of the disk 55 by means of links H that are inclined with respect to radial lines, the inner ends of the links being connected to the ring 88 by axially disposed pivots I06 and to the se 8 ments ofthe disk. 65 by means of axially disposed pivots I 07. of the ring 88 and the inner offset portion 68 of the ring 65, lying substantially in the plane of the outer portions of the disk 65, as shown in Fig. 8.

erly guide the radial movements of the segments.

The segments of disks 64 and 65 are guided by additional bolts I I2 that are arranged in pairs, each pair extending through registering slots I I3 in the disk 54 and in the inner portion 6 f the disk 65.

The intermediate, expansible disk 66 is composed of segments that are individually pressed outwardly by coil springs I I4 mounted in'recesses H5 in the segments of the disk 66 and bearing against the shoulder 69 on the inner disk 65. The extent of movement of the segments of the disk 55 with respect to the inner disk I55 is limited by pins I I5 secured to segments of the disk 66, which engage'in recesses H1 in the outer faces of the segments of the disk 65, as best shown in Fig. 10.

The initial bead forming operations By means of the devices above described, which are duplicated in the head C, the bead rings may be built into a fabric tire carcass on the drum A, the operations performed at opposite ends of the drum being identical and these operations Iceing performed simultaneously. The sequence of operations by which a bead ring is incorporated into the tire carcass is illustrated in Figs. 11 to 18 of the drawings. At the stage in the cycle of operations shown in Fig. 11, a fabric band D consisting of a plurality of plies of fabric has been applied to the periphery of the drum A, the band D being of a width to project a substantial distance beyond the ends of the drum, and a bead ring E with an attached flipper strip F has been mounted upon the seat 35 of the bead applying annulus 34. The disk 46 has been positioned between the annulus 34 and the end of the drum and the fabric folding ring 42 has been expanded from the position shown in dotted lines in Fig. 11 to the position shown in full lines, the e pansio of the ring 42 having been effected by movement of the sleeve 53 and disk 52 from the dotted line position to the full line position in Fig. 11.

After the ring 42 has been expanded as shown in Fig. 11, the'disk 46 is moved inwardly toward the drum A by means of the rods 56, to the position shown in Fig. 12. The sleeve 53 is held stationary in the position shown in Fig. 11 during the inward movement of the disk 45; and the disk 52 slides inwardly on the sleeve 53 to a position adjacent the flange 55 when the ring 42 is brought to the position shown in dotted lines in Fig. 12. The sleeve 53 is then moved outwardly to engage the flange 55 with the disk 52 and pull the links 4'! and 48 of .the toggle out of alignment so that the tension of the spring ring 42 snaps the ring to its-contracted position shown in full lines in Fig. 12, moving the arms 43 radially inwardly, swinging the links and 48 outwardly, and moving the disk 52 outwardly toward the collar 54 on the sleeve 53. The ring 42 is thus caused to snap inwardly against the exterior of the edge portion of the fabric band D, engaging the band simultaneously throughout the circumference thereof The links I05 overlie the inner faces 

